4. You have to pass priority in order to resolve Breakthrough, and if you do so, you will not have an opportunity to sacrifice Lion's Eye Diamond in the event your opponent chooses not to counter Breakthrough. Your only choice is to sacrifice Lion's Eye Diamond before you pass priority, but in that case, your hand will be discarded before your opponent chooses whether or not to use a counterspell.

im really excited, or tired its like 5 in the morning havnt slept in a while
So i was on another site and came across a decklist for mono blue artifact control and found and infinite mana combo and i wanna post it because i love combos
turn 2 infinite manaTolarian AcademyLiquimetal CoatingVoltaic Key
any other land

Against #2,
On the play, I play Nexus -> Key. He can't pact it because he'll die if he does. On his turn he plays his own key, which I will misstep. If he pacts my misstep, I'll combokill him. If he doesn't pact the misstep, he has no key, and thus can't pay for a casted pact or kill me in response to the trigger, so I will combo kill him anyway.

I like how Error's deck is barely legal since he only gets infinite mana turn 1 on the draw.

Yeah I'm not convinced there is a way to kill someone on turn 1 with 1 card in hand with no permanents, no library, and no mana in your mana pool. I offered a solution that wins with a library of cards, but I do not believe you can without it.